A method for locating devices within a network system

ABSTRACT

A method and apparatus for a communication system for facilitating communication on the network. Identification of a network device, preferably a controller or IO device, is based on a physical location of device. Accordingly, the physical location of the network device is determined by a device locator. The physical location of each network device is used to associate a network identifier, i.e., network address, with the network device to facilitate network communication with other devices. The network identifier is associated with the network device in response to a signal transmitted from the network device requesting the network identifier. A mapping method is used to convert a map of physical locations to one or more address tables so as to allow a controlling station to associate the network identifier with the network device for routing messages to and from the device based on the physical location.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This Application is a divisional of U.S. patent application Ser.No. 09/640,295, filed on Aug. 16, 2000, entitled Method and Apparatusfor Locating Devices within a Network System, which is acontinuation-in-part of a U.S. patent application, “Network AddressingBased On Physical Site Location Of A Network Device,” Ser. No.09/553,941, filed Apr. 21, 2000.

BACKGROUND OF INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates generally to a method forcommunication among a plurality of devices, such as input/output (IO)devices, in a network, such as a control/monitoring automation network.In particular, the present invention relates to establishing a networkidentity for each device.

[0004] 2. Background of the Invention

[0005] A local area network such as the Ethernet, can be used with acontrol system for industrial applications. Such a control system can beused to enable controllers, host computers, control devices such asvariable frequency drives, and other devices to communicate throughoutthe control system. The devices connected together in such acommunication link are generally referred to as “nodes.” Each node has aunique network identifier, i.e., Media Access Control (MAC) address,that facilitates network communication between the nodes.

[0006] In an automation factory where a plurality of automation devicesor input/output devices are used to perform a variety of intendedfunctions, each device has a controller, such as a programmable logiccontroller (PLC), to communicate with a controlling workstation or thePLC of another automation device. Furthermore, the PLC includes asoftware program to control the network device in performing theintended function. It is quite common to place network devices atphysical site locations in accordance with their particular functions.Conventionally, each of the network devices is identified by the MACaddress (or an Internet Protocol (IP) address) associated with thedevice. The network identifier is a fixed address which is given to adevice when it is manufactured or assigned by a user duringinterconnection with a network. The identifier, or MAC address, isunrelated to the physical site location of the device in the network.

[0007] If a PLC or other network device at a specific network locationis replaced by another PLC, the replacing PLC will not be operablyconnected to the network until its MAC address replaces the removedPLC's MAC address in the control system's application. This networkaddress constraint is disadvantageous in factory automation settings.For instance, if a problem arises with a network device, maintenancemust be performed by professional personnel skilled in networkingmanagement to administer implementing the new MAC address. This level ofinvolvement in network support is costly and time consuming. It istherefore advantageous and desirable to provide a method and a controlsystem wherein the need for maintenance of the network by professionallyskilled personnel is reduced or eliminated.

[0008] The present invention is provided to solve these and otherproblems.

SUMMARY OF INVENTION

[0009] A first embodiment of the present invention is directed to amethod of identification of a network device based on the physicallocation of the network device. The method comprises the steps ofidentifying the physical site location of a network device andassociating the physical location to the device address so as to allowthe device to communicate with other devices in the network.

[0010] Another aspect of the present invention is a control systemhaving a plurality of devices, wherein one or more devices include meansfor identifying the physical location so that the physical location isused as an identifier of the device in order to allow the device tocommunicate with other devices in the system. Preferably, a softwareprogram is used to convert a map of physical locations of the devicesinto an address table required for routing messages to the devices.

[0011] A further aspect of the present invention is a device to be usedin a control system wherein the device includes means for identifyingits own physical location so that the physical location can be used as anetwork identifier, i.e., address, of the device in order to allow thedevice to communicate with other devices in the control system.

[0012] Other features and advantages of the invention, which arebelieved to be novel and nonobvious, will be apparent from the followingspecification taken in conjunction with the accompanying drawings inwhich there is shown a preferred embodiment of the invention. Referenceis made to the claims for interpreting the full scope of the inventionwhich is not necessarily represented by such embodiment.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a block diagram showing a control system.

[0014]FIG. 2 is a block diagram showing a network device.

[0015]FIG. 3 is a block diagram showing a control system wherein aplurality of network devices share one physical location.

[0016]FIG. 4 is a block diagram showing a mapping method for relating aphysical location to the address of a network device.

DETAILED DESCRIPTION

[0017] While this invention is susceptible of embodiment in manydifferent forms, there is shown in the drawings and will herein bedescribed in detail preferred embodiments of the invention with theunderstanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intendedto limit the broad aspect of the invention to the embodimentsillustrated.

[0018] The control system of the present invention is shown in FIG. 1.As shown, the system 10 includes a plurality of network devices 101-105.Each of the network devices 101-105 is placed at one of the differentphysical locations 201-205, connected by a communication link 20. Thedevices include automation devices, IO devices, control devices, etc.The IO devices include, but are not limited to such machines as sensors,relays, gauges, valves, message displays, switches, limit switches,proximity switches, motor starters, motor controllers and any other likedevice as well as traditional I/O modules for PL C systems.

[0019] As shown in FIG. 2, each device has a controller such as aprogrammable logic controller (PLC) 116 for controlling the device incarrying out the intended function thereof. Preferably, the system 10 isa modified local area network (LAN) wherein the address of each deviceto be used for communication purposes is associated with the physicalsite location of the device, rather than a Media Access Control (MAC) oran Internet Protocol (IP) address that is usually associated with a PLCor to an input device of a PLC system. The control system can be anywired or wireless network, or any combination of the two, that useselectrical signals, optical signals or other forms of message signalingto convey information between devices in the system. The control systemcan also include one or more wide area networks (WANs). One of thenetwork devices 101-105 may be a workstation or a master module tooversee the overall operations of the control system.

[0020]FIG. 2 shows the components in a typical network device 100,representative of the network devices 101-105 shown in FIG. 1. As shownin FIG. 2, the network device 100 includes an I/O interface 122 forexchanging signals or data with a machine or a monitoring apparatus; anetwork interface 112 to exchange signals or data with other networkdevices in a control system; a device locator 114 residing inside oroutside the network interface 112 to identify the physical location ofthe network device 100; and a programmable logic controller PLC 116 tocontrol the machine or monitoring apparatus to which the network device100 is connected using an application program 120 stored in a memoryunit 118. These components can communicate with each other and othernetwork devices 100 through a bus in the backplane 124.

[0021] In a factory automation system where a variety of automationmachines are organized into a control system, and each automationmachine is controlled by a network device 100, each machine may have aparticular function to perform. For example, one machine may perform ametal stamping function while another performs metal surface polishingin an assembly line environment. Thus, the network device 100 connectedto each automation machine includes an application program 120 tocontrol the machine. In order for the machine to carry out the intendedfunction in a timely manner, the network device 100 must have theability to communicate with other network devices in the system.

[0022] It should be noted that in some applications the machinesconnected to a network are required to perform different functions. Butin other applications, all machines can be used to perform the samefunction. For example, in a pipeline where batches of refined petroleumproducts are transported within a transport pipe from one state toanother, a number of instruments are used at different locations alongthe pipeline to monitor the flow rate, fluid pressure and the content ofthe passing batch. Thus, all the monitoring instruments and theapplication program therefor can be identical. The only difference isthe location of the monitoring instruments. In this type of theapplication, it is advantageous to use the physical site location as theaddress of each monitoring instrument.

[0023] In general, when the automation factory is designed, theindustrial engineer works off of a floor plan. The floor plan is refinedto an individual device or machine and to the physical site location ofthe device. This physical location becomes the network identifier, oraddress, of the unit in the network control system. Once the networkdevices are installed according to the floor plan, a software program isused to associate the location of the devices on the floor plan to thelocation of the devices as identified by the device locator 114 of thenetwork device 100 to which the network device is operably connected.Because the device locator 114 only recognizes the location of thedevice and not its function, the network device 100 connected to onemachine can be identical to the network device 100 connected to anothermachine. Thus, all network devices 101-105 as shown in FIG. 1 can beidentical. Once identified, all control or application programs andconfiguration information needed for an automation machine placed at aparticular location to perform an assigned function can be downloadedfrom a master module, to the PLC 116 of the network device 100.Preferably, a mapping method is used to convert a map of the physicalsite locations of the network devices into one or more address tablesrequired to route network messages to these devices. Such a mappingmethod utilizes the physical location of a network device similar to theMAC or IP address of the device with regard to the routing of messagesin the network. The mapping method will be described in conjunction withFIG. 4.

[0024] Additionally, network configuration information or monitor,control and application programs can be mapped to physical sitelocations. Dependent upon the location of the network device, variablesoftware application can be downloaded and input into the networkdevice.

[0025] If a problem occurs with a network device 100 on a certainautomation machine, that network device 100 can be replaced with anothernetwork device 100. Likewise, if a problem develops with a certainautomation machine, it can be replaced with another similar machine,with or without changing the network device 100. Once the replacement iscompleted, the programs and configuration information can be downloadedagain according to the physical site location as determined by thedevice locator of the replacement network device. Because the physicallocation of the automation machine remains the same, the programs orconfiguration information downloaded to control the automation machinewill always be the same. Replacing a machine with a similar machine orreplacing a network device on a machine will no longer not require theskill of a network management personnel to modify the applicationprograms with respect to the network address. Thus, the maintenance ofan automation factory is significantly simplified and can be carried outin a less costly manner.

[0026] As an additional benefit of the present invention, the locationinformation can be used as a safety check to assure that the applicationintended to be executed in the network device is correct. It is notuncommon where a user places the wrong PLC program into a PLC and thewrong PLC causes an unintended operation. By double-checking thephysical location, most mistakes of this type can be eliminated.

[0027] The device locator 114 is known in the art. Global positioningtechnology such as angle and time difference of a signal's arrival(TDOA), Personal Locator System (PLS), global positioning system (GPS)and assisted GPS are well known. The GPS incorporates a constellation ofsatellites and employs signal timing to determine a physical location.The assisted GPS utilizes stationary servers throughout a coverage areato assist the position locator receiver to acquire the GPS signals. Anyone of these global positioning techniques, or any other globalpositioning technique, can be integrated in the control system toidentify the location of the network device 100. However, each of theselocator devices or systems has a location resolution beyond which thelocator is unable to resolve. For example, a location resolution of fivesquare feet or better may be impractical in a factory automation settingwhere two or more machines are located closely together.

[0028] In another embodiment of the present invention as shown in FIG.3, one physical locator can be shared with a group of machines locatedin a small footprint. A network 10′ comprises a group of network devices101, 105, 106, 107 and 108, and a controlling workstation 119. While thedevices 101 and 105 are separately positioned in physical locations 201and 205, respectively, the devices 106-108 are seemingly located in thesame physical location 206 due to the physical locator's resolution. Insuch implementation, each device 106 can have its own device locator 114or one device locator can be shared by the devices 106 However, the PLC116 (see FIG. 2) in each of the network devices 106-108 must have itsown specific network identifier, i.e., MAC or IP address.

[0029] When a PLC 116 is powered on, it learns its location from thedevice locator 114 and then transmits a message, providing both its MACaddress and the physical location to the controlling workstation 109.The message transmitted from the PLC 116 to the controlling workstation109 can be a Reverse Address Request Protocol (RARP) message. A softwareprogram in a controlling workstation 109 then translates the message inorder to map the floor plan with the provided MAC addresses for theassociated machines. As such, the controlling workstation 109 or anotherdevice can download an appropriate application program to the PLC, andthe PLC will start with the application program intended for a networkdevice in the shared location.

[0030] Whether each network device 100 is positioned in a differentphysical site location as shown in FIG. 1, or a number of networkdevices 100 share a physical site location as shown in FIG. 3, it isadvantageous to link a map of the physical locations to one or moreaddress tables for routing messages to or from the network devices. Sucha mapping method is shown in FIG. 4. As shown in FIG. 4, a map 300having six different physical locations is related to an address table310 having six different network addresses. For example, physicallocation 1 is associated with network address 1, etc. Depending on thenetwork designer, the network address can be a MAC address, an IPaddress or any other type of network identifier. Preferably, the mappingbetween the physical site location and the network address is performedby an application program in the control system.

[0031] The present invention can be applied to a variety of control andmonitoring applications. For example, a utility company can use thenetwork device associated with a meter to remotely communicate with themeter at any location without the need of identifying the meter. Thenetwork device can be programmed to automatically convey informationincluding its physical location and the meter information to the utilitycompany according to a stored instruction. Similarly, a pipeline companycan monitor and control the flow of the material at desired locationsand time intervals. A water company can monitor water usage for billingand leak detection. A mining company can use a plurality of networkdevices which can be easily relocated at the user's discretion to reportthe status of air quality, water levels, etc. Network devices can beinstalled along with various control and monitoring instruments atvarious locations in a building to communicate local temperature,humidity, air quality, lighting condition, etc. In a smaller scale, thepresent invention can also be applied to home automation.

[0032] It will be understood by those skilled in the art that numerouschanges and deviations in the form and detail thereof may be madewithout departing from the spirit and scope of the present invention.For example, the control system as depicted in FIG. 1 can be replaced bya wireless network, a wired and wireless network, or a network with aplurality of gateways and bridges. Similarly, the device as depicted inFIG. 2 can be modified to include more components or to reduce thenumber of components. However, these variations do not depart from thescope of the present invention wherein network addressing is based,partially or completely, on the physical site location of the devices inthe control system network.

[0033] Thus, the present invention has been described with respect tothe preferred embodiments thereof. While specific embodiments have beenillustrated and described, numerous modifications come to mind withoutsignificantly departing from the spirit of the invention and the scopeof protection is only limited by the scope of the accompanying claims.

I claim:
 1. A method of communicating with a controller in acommunication system, the method comprising the steps of: identifying alocation of the controller, the controller having a medium accesscontrol (MAC) address; transmitting a reverse address request protocol(RARP) message, the message including the location of the controller andthe medium access control address of the controller; translating theRARP message into a network identifier; and, associating the networkidentifier with the controller.
 2. The method of claim 1 furthercomprising transmitting an application program to the controller, theapplication program is selected in response to the network identifier.3. The method of claim 1 wherein a controlling device translates themessage into a network identifier, the controlling device includes afloor plan of the communication system.
 4. The method of claim 1 whereinidentifying the location of the controller comprises using a globalpositioning system.
 5. The method of claim 1 wherein the identifying thelocation of the controller comprises using an assisted globalpositioning system.
 6. A method of communicating with an IO device in acommunication system, the method comprising the steps of: identifying alocation of the IO device, the IO device having a medium access control(MAC) address; transmitting a reverse address request protocol (RARP)message, the message including the location of the IO device and themedium access control address of the IO device; translating the RARPmessage into a network identifier; and, associating the networkidentifier with the IO device.
 7. The method of claim 6 furthercomprising transmitting an application program to the IO device, theapplication program is selected in response to the network identifier.8. The method of claim 6 wherein a controlling device translates themessage into a network identifier, the controlling device includes afloor plan of the communication system.
 9. The method of claim 6 whereinthe step of identifying the location of the I/O device further comprisesusing a global positioning system.
 10. The method of claim 6 wherein thestep of identifying the location of the I/O device further comprisesusing an assisted global positioning system.